An international team of researchers examined adult dietary habits and found that Americans are cutting back on low-quality carbohydrates. However, intake remains high at over 40 percent, while the consumption of saturated fat remains well above the national recommendation.
"Although there are some encouraging signs that the American diet improved slightly over time, we are still a long way from getting an 'A' on this report card," said coauthor Fang Fang Zhang, a nutrition researcher at the Friedman School of Nutrition Science and Policy at Tufts University.
"Our study tells us where we need to improve for the future."
Unhealthy macronutrient sources undermine small gains
For their study, the researchers wanted to know from which dietary sources Americans usually get their protein, carbohydrates and fats. Hence, they looked at the diets of about 44,000 adults who participated in the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2016. NHANES is a program of studies designed to assess the health and nutritional status of American adults and children. The participants self-reported their diets during the study period.
The team measured the participants' nutrient intake using the standards laid out by the Department of Agriculture's Food and Nutrition Database for Dietary Studies. They also assessed the participants' overall diet quality through the Healthy Eating Index, which measured how well a set of foods aligned with national recommendations.
The researchers found improvements in the average American's diet, noting that many succeeded in cutting back on low-quality carbohydrates by three percent. Total carbohydrate intake also decreased by two percent, while consumption of high-quality carbohydrates increased by one percent.
But these were modest gains, according to the researchers, since 42 percent of the participants' daily energy intake came from low-quality food sources, particularly processed grains and added sugars. In contrast, only nine percent of their daily energy intake came from high-quality sources, such as whole grains and whole fruits.
Moreover, the participants' total saturated fat intake accounted for 12 percent of their daily calories, exceeding the recommended amount of 10 percent daily. The researchers also revealed that total fat intake went up by one percent, with saturated fat making up half of the total. According to studies, consuming large amounts of saturated fat can elevate bad cholesterol levels, increase the risk of heart disease and cause a person to put on an unhealthy amount of weight.
In addition, the researchers found that the top protein sources were red and processed meat. Protein obtained from seafood and plant-based sources comprised a much smaller proportion. (Related: Consequences of the American Processed Foods Diet.)
"Our research suggests that Americans have an opportunity to diversify their sources of protein to include more seafood, beans, soy products, nuts and seeds," said Shilpa Bhupathiraju, one of the study's senior authors.
It's worse for the old and the poor
The researchers also found that dietary improvements were less pronounced for older people and those of lower socioeconomic status.
While adults with high incomes decreased their intake of low-quality carbohydrates by four percent, those living below the poverty line decreased their intake by only two percent. And although most Americans are eating better, the researchers found no improvements among adults over 50 years old, those living below the poverty line and people with less than a high school education.
"These findings also highlight the need for interventions to reduce socioeconomic differences in diet quality, so that all Americans can experience the health benefits of an improved diet," said Zhang.
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